EP1340565B1 - Device for the continuous casting of a strip from a molten metal - Google Patents

Abstract

Device for casting molten metal, especially molten steel, into cast strips comprises: casting rollers (2, 3) rotating in the opposing direction in the casting operation; a conveying path (6) for removing the cast strip leaving the casting gap (4) between the rollers; and a casting roller screen (9) into which the strip leaving the casting gap enters an inlet opening (15). The screen surrounds a cooling zone (K) in which a temperature prevails during the casting operation which is lower than the temperature of the gases heated by the cast strip. An Independent claim is also included for a process for casting molten metal, especially molten steel, into cast strips. Preferred Features: The screen is arranged in the conveying direction of the cast strip below the casting rollers. One of the walls of the screen is cooled using a fluid.

Description

The invention relates to a device for the continuous casting of molten metal, in particular molten steel, to cast strip. When casting steel in such as "double roller" or "two-roller casting machines" designated devices are each two during the casting counter-rotating, axially parallel arranged and internally cooled casting rolls present, which limit the longitudinal sides of a casting gap formed between them. In each case, so much liquid melt is poured into this casting gap that a melt sump is formed above the casting gap. The melt coming from this sump onto the casting rolls solidifies and is conveyed by the casting rolls into the casting gap. In the casting gap, the cast strip is formed from the shells thus formed on the casting rolls and still free-flowing melt, which is then removed and fed to further processing.

Since the cast strip has high temperatures when it leaves the casting gap, scale forms on its surface in contact with the environment in large quantities of scale. This scale hinders the continuous processing of the tape. In particular, the tinder influences that Work result in the hot rolling continuously performed on the casting of the strip negative.

Various solutions for reducing the scale of scaling have been proposed. Thus, it is known to arrange a housing in devices of the type in question below the Gießspaltes in which an oxygen-reduced, inert gas atmosphere is maintained during the casting operation.

In addition, for example, in the EP 0 830 223 B1 has been proposed, in conjunction with a complete enclosure to cool the cast strip on leaving the casting gap contactless, in order to avoid contact of the strip at high temperatures with the environment. For this, the points from the EP 0 830 223 B1 known device to an enclosure that completely and large volume surrounds the casting rolls and the cast strip emerging from the casting gap defined by them on its way to a hot rolling stand. In a region formed below the casting rolls, the side walls of the housing run towards each other in a funnel shape, so that the cast strip passes through a narrowed passage opening into the subsequently traversed space of the enclosure. The funnel-shaped converging walls are in this case occupied by cooling elements which are intended to effect the desired cooling of the strip emerging from the casting gap. However, the radiated heat from the cast strip and the gases forming on it pass unimpeded to the casting rolls and their storage and their drive required, surrounded by the housing components.

In addition to the problem of scale formation causes such direct thermal radiation in the operation of the known casting machines the difficulty that it comes from the cast strip heat radiation to a considerable heating of the components located in the radiation area of the casting machine. This heating leads on the one hand to a deformation of the casting rollers carrying carrier. These deformations make it particularly difficult to ensure the dimensional accuracy of the cast strip, when the respective carrier are designed as a removable roll for transportable frame. On the other hand, the high temperature in the region of the casting machine leads to a considerable burden on the staff monitoring the casting operation.

The invention had for its object to provide a device of the type described above, in which the load is reduced by emitted from the cast strip heat.

This object has been achieved by a trained according to claim 1 device.

With a device according to the invention, molten metal, in particular molten steel, is cast into a cast strip in that the molten metal is poured into a strip in a casting gap formed between two casting rolls which rotate in opposite directions in the casting operation and transported away via a conveying path, wherein the cast strip as it leaves the casting gap, similar to the prior art, passes through a cooling zone in which a temperature lower than the temperature of the gases heated by the cast strip is maintained.

In a device according to the invention, a zone is formed close to the outlet region of the casting gap, in which a targeted lowering of the temperature is brought about. As a result of this cooling, the natural, thermally induced flow ("chimney effect") is interrupted in which the gases heated by the cast strip during its transport via the conveying path ascend counter to the conveying direction of the strip. In the process according to the invention, the cooling zone forms a barrier which prevents the hot gases heated by the strip from reaching the components required to support the rolls. The unavoidable in conventional strip casting devices as a result of the heating of the gases chimney effect is counteracted so effectively.

The effect of the cooling zone is assisted in a device according to the invention in that it is bounded by a pointed roof-shaped Gießwalzenabschirmung. On the one hand, this shielding constitutes a physical obstacle by which the flow of hot gases to the rollers or to a work platform, for example in the area of the rollers, is interrupted. At the same time the Gießwalzenabschirmung is available for targeted cooling of existing in its bounded space gases available. The one at Shielding according to the invention allows in this way a particularly effective protection of the casting rolls, the components required for their storage and their operation, and all other aggregates arranged in the vicinity of the casting rolls. Similarly, the Gießwalzenabschirmung combined with the inventive cooling of the gases in the cooling zone leads to a significant reduction in the risk of personnel employed in the casting rolls.

The formation of a cooling zone in the area bounded by the Gießwalzenabschirmung can be generated, for example, characterized in that at least one of the walls of the Gießwalzenabschirmung is fluid cooled. For this purpose, the cooled wall may have at least one cooling passage through which the cooling fluid flows during the casting operation. On the one hand, such liquid cooling ensures that the heat acting on the casting roll shield is dissipated quickly and effectively. At the same time, the cooling of the casting roll shield results in intense cooling of the gases impinging on the casting roll shield. These cooled gases mix with the hot gases flowing in the area bounded by the casting roll shield, so that they too are cooled and a zone of lower temperature is established.

The formation of the cooling zone can also be particularly effectively supported by the fact that at least one device for injecting cooling gas in the Cooling zone is provided. In this case, the effect of the cooling gas can be further improved by the fact that the flow of the injected into the cooling zone cooling gas is directed against the flow direction of the heated strip from the cast gas. Such an orientation of the cooling gas flow leads to an intense mixing of the hot gases with the cooling gases, so that within a short time a particularly effective cooling zone constructed and the rise of hot gases on the Gießwalzenabschirmung addition is particularly safe prevented. The effectiveness of the cooling gas flow can be increased further by sweeping over the surface of the cast strip. In this way, not only the rising, heated by the cast strip gases, but also the tape itself are cooled and reduces the heat radiation emitted by it, with the result that also less heated with the band in the course of the further conveying path in contact gases become. At the same time, the gas flow directed against the surface of the belt forms, in addition to the thermal barrier, a fluidic barrier by which the rise of hot gases directly at the surface of the belt is also suppressed.

The cooling of the strip achieved in the region of the cooling zone reduces the amount of scale formed on the strip surface during the transport of the strip. The formation of scale can be further suppressed in such cases in which a cooling gas is blown into the cooling area, in that an inert gas is used as the cooling gas. By the blowing of an inert gas into the cooling zone not only achieves a cooling of the strip surface, but also a contact of the surface of the cast strip with the atmospheric oxygen of the environment and concomitantly the formation of larger scale layers on the strip surface is effectively counteracted. An undesirable for many applications carburizing the belt can also be counteracted by the fact that, alternatively or in addition to the injection of inert gas, a reducing acting cool gas is blown into the cooling zone.

By virtue of the fact that the casting roll shield extends in a pointed roof shape into the space defined below the casting gap by the casting rolls, an embodiment optimized with regard to its protective effect of the casting roll shield itself is achieved. In this case, the inlet opening for carrying out the cast strip emerging from the casting gap is preferably formed in the ridge region of the casting roll shield. By such a pointed roof-shaped, adapted to the shape of the outlet area in the embodiment of the Gießwalzenabschirmung it is possible to shield both the casting rolls and arranged in their neighborhood components and aggregates, as far as possible completely against the cast strip. If the local conditions do not permit such a close arrangement of rolls, casting roll shield and cast strip, it is alternatively possible to arrange the edges of the inlet opening of the casting roll shield axially parallel to the casting rolls at a small distance from the casting rolls. In this In the case of the casting roll shield provided according to the invention, in the region of the casting rolls, only a lateral boundary of the cooling zone is formed, while its upper boundary is formed by the casting rolls themselves.

In principle, it is advantageous if the cross-sectional area of the inlet opening of the casting roll shield is adapted as closely as possible to the cross section of the cast strip. Even in this way, the escape of gases from the inlet opening can be effectively hindered.

Regardless of how the Gießwalzenabschirmung is formed, it is advantageous if in each case nozzles are present in the region of the inlet opening, from which emerges in the casting operation, a gas stream, which counteracts the escape of gas from the inlet opening. When the inlet opening with its edges closely surrounds the cast strip leaving the casting gap, this can be achieved, for example, by directing a gas flow in the manner of an air jet knife against the strip. If, on the other hand, the sealing of the inlet opening with respect to the casting rolls is carried out, a gas jet can be directed in a corresponding manner against the rolls. Depending on the local conditions, it is possible to use flat-jet nozzles or round-jet nozzles arranged over the width of the strip or the rolls, whose jets are associated with one another such that an aspiration of gases, in particular air, from the environment of the device designed according to the invention into that of the Castor shield shielded cooling zone is prevented.

According to another particularly practical embodiment of the invention, it is provided that the Gießwalzenabschirmung is supported by a bearing of the casting rolls supporting, transportable from a working position to a waiting frame. With such a mounting of the Gießwalzenabschirmung to the frame, the frame with the rollers and the Gießwalzenabschirmung can be exchanged as a complete unit at a roll change. Thus, after transporting the frame from the working position to the waiting position, not only the rolls themselves can be serviced, but also the casting roll shield and the aggregates provided, for example, for cooling the walls of the casting roll shield and for injecting the cooling gases onto the casting roll shield. This proves to be particularly useful if the Gießwalzenabschirmung is assigned to support their heat-insulating effect on their cast tape associated surfaces with refractory material.

If, in a manner known per se, an enclosure is provided which at least partially surrounds the conveying path of the cast strip, then it is favorable if the cast roll shield is placed on such a housing or is part of such an enclosure. The enclosure preferably encloses the conveying path of the cast strip at least up to a first pair of rolls arranged in the conveying path for conveying or hot rolling the strip. This embodiment of the invention proves to be particularly useful if in the enclosure to suppress the formation of scale an inert atmosphere is maintained.

If the casting roll shield forms part of an enclosure, it is advantageous in view of the possibility of simple, regular maintenance if the casting roll shield is detachably connected to the enclosure. This is especially true when the Gießwalzenabschirmung is connected in the manner already mentioned with a transportable frame. It should be present between the Gießwalzenabschirmung and the housing a seal. Such a seal, which at the same time withstands the thermal stresses in the region of the casting device, can be accomplished in that it is in the form of a sand-filled channel in which the Gießwalzenabschirmung stands with its lower edge.

The load on the units and components of the casting device can also be further reduced by the fact that a suction device for sucking the heated of the cast strip gases is present. In the event that an enclosure of the transport path of the cast strip is provided, the housing may have a suction opening to which the suction device is connected.

Fig. 1

eine Vorrichtung zum Vergießen von Stahlschmelze zu gegossenem Band in einem ersten Längsschnitt,

Fig. 2

die Vorrichtung zum Vergießen von Stahlschmelze in einem zweiten Längsschnitt.

Further advantageous embodiments of the invention are specified in the dependent claims and are described below with reference to an embodiment illustrative drawing explained in more detail. They show schematically:

Fig. 1

a device for pouring molten steel into cast strip in a first longitudinal section,

Fig. 2

the apparatus for casting molten steel in a second longitudinal section.

The apparatus 1 for pouring a molten steel into a cast steel strip B has two casting rolls 2, 3 arranged parallel to one another and rotating in opposite directions, which delimit the longitudinal sides of a casting gap 4 formed between them and the melt sump 5 arranged above them, into which the molten steel is introduced , The two lateral, of the casting rolls 2.3 free transverse sides of the casting gap 4 and the melt sump 5 are each sealed by side seals not shown here in detail. During casting, the casting rolls 2, 3 are continuously cooled by a stream of cooling water.

The cast steel strip B withdrawn from the casting gap 4 is transported via a conveying path 6 to a hot rolling stand 7 in which it is hot-rolled continuously to form a hot strip W having a certain final thickness. In this case, the conveying path 6 has a first section extending essentially vertically from the casting gap 4, which then merges in an arc into a second section extending essentially horizontally to the hot rolling stand 7.

The conveying path 6 is up to the hot rolling stand 7 substantially completely surrounded by a housing 8, which shields him from the environment so that only the hot rolled hot strip W comes in direct contact with the ambient air outside the housing 8. The upper part of the housing 8 associated with the casting rolls 2, 3 is formed by a casting roll shield 9, which is detachably placed on the upper edge of the main part 10 of the housing 8 which is substantially larger than the casting roll shield 9. For this purpose, a sand-filled groove 11 is formed on the upper edge of the main part 10, in which the Gießwalzenabschirmung 9 sits with its main part 10 associated lower edge region. The channel 11, together with the sand contained in it, forms a seal in which the sand contained in the channel 11 ensures that ambient air does not enter the interior space 12 enclosed by the housing 8 in the region of the channel 11.

Both the Gießwalzenabschirmung 9 and the main part 10 of the housing 8 are lined on the conveying path 6 associated inner sides with a layer 13 of refractory material. By the layer 13, on the one hand, the thermal load on the existing example of steel outer wall of the enclosure is reduced. On the other hand, the layer 13 also forms an insulation, by means of which the heat radiation acting on the environment from the enclosure 8 is reduced.

The Gießwalzenabschirmung 9 is pointed roof-shaped in such a way that their respective casting rolls 2.3 associated walls 9a, 9b pointed in the direction of the casting gap 4 are formed tapering towards each other and extend to just below the casting rolls 2.3. In its the main part 10 of the housing associated edge region, the Gießwalzenabschirmung 9 has a frame portion of low height, with which it sits in the groove 11. The housing 8 and with it the Gießwalzenabschirmung 9 thereby extend laterally beyond the width of the cast steel strip B, wherein the enclosure is closed in its over the width of the casting rolls 2,3 protruding part.

In the project beyond the width of the casting rolls 2.3 part 9 cooling channels 14 are formed in the walls 9a, 9b of the Gießwalzenabschirmung through which in the casting operation also continuously a cooling water flow is passed. In this way, the walls 9a, 9b are cooled at least as well as the casting rolls 2, 3 (FIG. Fig. 2 ).

In the region of the casting rolls 2, 3, an inlet opening 15 is formed in the casting roll shield 9, through which the cast steel strip B is led into the enclosure 8. The upper, formed on the frame portion edges 16,17 of this inlet opening 15 are axially parallel and at a small distance to the casting rolls 2,3. On the edges 16,17 each flat jet nozzles 18,19 are arranged, from which in the manner of an air knife inert gas is blown against the respective casting roll 2 and 3 respectively. In this way, a contactless sealing of the existing between the upper edges 16,17 and the casting rolls 2,3 gap at the same time unrestricted mobility of the casting rolls 2,3 made by the the penetration of ambient air into the housing 8 is prevented ( Fig. 1 ).

In addition, the Gießwalzenabschirmung 9 carries on the interior 12 of the housing 8 associated side of its walls 9a, 9b respectively nozzles 20,21, from which in the casting operation each consisting of an inert gas or a mixture of an inert gas and a reducing gas gas stream G in the Interior 12 of the enclosure 8 is blown. The nozzles 20,21 are aligned such that at least a portion of the gas flow G exiting them sweeps over the surface of the cast steel strip B.

With a distance below the channel 11, an opening is formed in a side wall of the housing 8, to which a suction pipe leading to a suction device, not shown, is connected.

The Gießwalzenabschirmung 9 is attached to a frame 23 which carries the casting rolls 2,3 and other, not shown here aggregates, which are needed for supplying and for driving the casting rolls 2,3. The frame 23 can be transported with its supported casting rollers 2,3, the Gießwalzenabschirmung 9 and the other units from its working position shown in the figures in a standby position, not shown, are carried out in the maintenance.

During the casting operation, the cast steel strip B is continuously withdrawn from the casting gap 4 and also continuously via the conveying path 6 to the hot rolling mill 7 promoted. In this case, prevails in the housing 8 an inert gas atmosphere by which the formation of scale on the surface of the cast steel strip B is suppressed. The gas coming into contact with the hot cast strip, contained in the enclosure 8, is heated and rises as hot gas flows T as a result of its temperature increase counter to the direction of conveyance F in the enclosure 8.

Meanwhile, via the nozzles 20, 21 further intergas is continuously blown at a low temperature into the cooling zone K formed in the conveying direction F of the cast steel strip B below the casting roll shield and laterally delimited by it. In this case, the injected gas stream G sweeps over the surface of the cast steel strip immediately after its exit from the casting gap 4, so that a targeted cooling of the strip surface is effected.

By blowing in the cool gas stream G, cooling the surface of the cast steel strip B and continuously cooling the walls 9a, 9b of the casting roll shield 9, a temperature lower than the temperature of the hot gas stream T is continuously maintained in the cooling zone K. in the cooling zone K reaching, mixed with the cooling gas flow G hot gas flow T is cooled as a result, so that its rise movement is interrupted. The gas volumes accumulating in front of the cooling zone K and formed from the gas flows G and T are sucked off via the suction pipe 22.

The formation of the cooling zone K, which is bounded by the casting roll shield 9, in the immediate vicinity of the casting rolls 2, 3 prevents the hot gas stream T from heating the frame 23 and the assemblies and devices attached to it or endangering the persons employed by the device 1 ,

At the same time, the continuous cooling of the walls 9a, 9b of the casting roll shield ensures that, despite the heat radiation emitted by the cast steel strip, they are so little thermally stressed that they retain their shape even during the casting operation. In this way, a permanently tight seal between the casting rolls 2, 3 and the edges 16, 17 of the outlet opening 15 is ensured.

Finally, by injecting inert cooling gas into the enclosure 8, the formation of large amounts of scale on the surface of the cast steel strip B is suppressed.

As a result, it is possible to produce a cast steel strip B which has a surface finish which minimizes stress on the device used for its production and on the personnel working on this device, making it particularly suitable for further processing.

REFERENCE NUMBERS

1

Device for casting a molten steel S

2.3

casting rolls

4

casting gap

5

melting swamp

6

conveying

7

Hot rolling mill

8th

housing

9

Gießwalzenabschirmung

9a, 9b

Walls of the casting roll shield 9

10

Main part of housing 8

11

sand-filled gutter

12

Interior of the enclosure 8

13

Layer of refractory material

14

cooling channels

15

inlet opening

16.17

upper edges of the inlet opening

18.19

Flat spray nozzles

20.21

jet

22

suction tube

23

frame

B

cast steel band

F

conveying direction

G

gas flow

K

cooling zone

T

Hot gas streams

W

hot strip

Claims (22)

1. Device for pouring metal melts, in particular steel melts, to form cast strip (B)

   - with cast rollers (2, 3) which counter-rotate during the casting process, said cast rollers delimiting the longitudinal faces of a casting gap (4) formed between said cast rollers;

   - with a conveying route (6) for leading away the cast strip (B) emanating from the casting gap (4) and

   - with a cooling zone (K), formed in the conveying direction of the strip (B) below the casting gap (4), in which during casting the temperature is lower than the temperature of the gases heated by the cast strip (B), characterised in that the cooling zone (K) is formed in a cast roller shielding device (9) in the shape of a pointed roof, into which the strip (B) emanating from the casting gap (4) enters through an entry aperture (15), and the walls (9a, 9b) of which extending along the cast rollers (2, 3) extend tapering onto one another in the direction of the casting gap (4) into the space which delimited by the cast rollers (2, 3) is present below the casting gap (4).
2. Device according to Claim 1, characterised in that the cast roller shielding device (9) is arranged in the conveying direction of the cast strip (B) below the cast rollers (2, 3).
3. Device according to any one of the preceding claims, characterised in that at least one of the walls (9a, 9b) of the cast roller shielding device (9) is fluid-cooled.
4. Device according to Claim 3, characterised in that the cooled wall (9a, 9b) comprises at least one cooling channel (14) through which the cooling fluid flows during the casting process.
5. Device according to any one of the preceding claims, characterised in that at least one device (20, 21) is provided for injecting cooling gas (G) into the cooling zone (K).
6. Device according to Claim 5, characterised in that the flow of the cooling gas (G) injected into the cooling zone (K) is directed against the direction of flow of the gases (T) heated by the cast strip.
7. Device according to Claim 5 or 6, characterised in that the injected cooling gas (G) moves over the surface of the cast strip (B).
8. Device according to any one of Claims 5 to 7, characterised in that the cooling gas (G) is inert.
9. Device according to any one of Claims 5 to 7, characterised in that the cooling gas (G) has a reduction effect.
10. Device according to any one of the preceding claims, characterised in that the opening cross section of the entry aperture (15) of the cast roller shielding device (9) is adapted to the cross section of the cast strip (B).
11. Device according to any one of the preceding claims, characterised in that the edges (16, 17) of the entry aperture (15) of the cast roller shielding device (9), which edges (16, 17) extend parallel to the axis of the cast rollers (2, 3), are arranged in close proximity to the cast rollers (2, 3).
12. Device according to any one of the preceding claims, characterised in that in the region of the entry aperture (15), there are nozzles (18, 19) in particular fan nozzles and/or circular section nozzles, from which during the casting process a gas stream emanates which counteracts the issue of gas from the entry aperture (15).
13. Device according to any one of the preceding claims, characterised in that the cast roller shielding device (9) extends in the direction of the width of the cast strip (B) at the sides of the cast rollers (2, 3).
14. Device according to any one of the preceding claims, characterised in that the cast roller shielding device (9) is carried by a frame (23) which can be moved from an operating position to a standby position, said frame supporting the bearings of the cast rollers (2, 3).
15. Device according to any one of the preceding claims, characterised in that the surfaces of the cast roller shielding device (9), which surfaces face the cast strip (B), are covered by fireproof material (11).
16. Device according to any one of the preceding claims, characterised in that the cast roller shielding device (9) forms part of a housing (8) which encloses the conveying route (6) of the cast strip (B) emanating from the casting gap (4) in the direction of conveyance (F), at least along a section starting from the exit region of the casting gap (4).
17. Device according to Claim 16, characterised in that the housing (8) encloses the conveying route (6) of the cast strip (B) at least to a first device (17), arranged in the conveying route (6) for leading away or hot rolling the strip (B).
18. Device according to either of Claims 16 and 17, characterised in that the cast roller shielding device (9) is removably connected to the housing (8).
19. Device according to Claim 18, characterised in that there is a seal between the cast roller shielding device (9) and the housing (8).
20. Device according to Claim 19, characterised in that the seal is designed as a gutter (11) filled with sand, with the bottom edge of the cast roller shielding device (9) standing in said gutter.
21. Device according to any one of the preceding claims, characterised in that there is an extraction device for extracting the gases (T) heated by the cast strip (B).
22. Device according to Claim 21 and any one of Claims 16 to 20, characterised in that the housing (8) comprises an extraction aperture (22) to which the extraction device is connected.

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